204 MK. J. PARKINSON ON THE GEOLOGY [Maj* : 



III. Contact of Limestone and Pyroxene-Graniilite. 



Railway between Matale and Ukuwela. — On leaviug- 

 Matale Station we see, first, a few outcrops of white crystalline 

 limestone, followed and overlain by hard red soil. This exhibits a 

 number of small ferruginous concretions, which are, however, merely 

 the outcome of a weathered condition, for internally it is mottled 

 red and yellow, and is apparently an argillaceous soil rich in iron. 



In a short distance we come to a level crossing, and on the left- 

 hand side of the track a small section is disclosed by the railway- 

 cutting. The dominant rock is a crystalline limestone, but in this, 

 and looking like an approximately horizontal dyke, is a fine- 

 grained rock rather saccharoidal on a fractured surface, but with a 

 greasy lustre. This ver}- closely resembles the pyroxene-granulites 

 exposed on the road to Hakgala from Newara Eliya (see p. 207). 

 This rock, which I will call * the Band,' in order not to prejudge 

 the question of its intrusive nature, is about 4 inches thick at the 

 only place where its upper and lower surfaces are seen. It can be 

 traced for about 5 yards, the base not being seen; and iu one 

 place it forks, and partly includes a mass of limestone about a 

 yard square. 



After this exposure, we find a good cutting of well-crystallized 

 limestone (specific gravity =2*86), followed by another of red rock 

 similar to that seen before, but less concretionary on the weathered 

 surface. This is succeeded in turn by limestone, and again by the 

 red soil, which must be a kind of laterite. 



Thin sections from the ' Band ' and limestone will now be 

 described. In a slide cut from a specimen of the former (specific 

 gravity =2*96) the dominant mineral is a pleochroic augite. In an 

 orthopinacoidal section the colour for vibrations normal to the 

 prismatic cleavage is a pale pink with a slight tinge of crimson : at 

 right angles a pale, rather bluish, green. The pleochroism thus 

 closely resembles that of hyperstheue. The polarization- tints are 

 brilliant, rather recalling those of olivine. Occasionally this augite 

 is of a medium shade of sage-green, non-pleochroic or but feebly so,. 

 and probably merely a variety. Mixed in with this augite are a few 

 irregular grains of pale red garnet, which are absent in a second 

 slide. The augite is altering to brown hornblende, the pleochroism 

 of which ranges from a yellow to a red-brown. There are also a few 

 grains of pyrites. Brown mica occurs in other specimens. These 

 darker minerals constitute the greater part of the rock. The rest of 

 the slide is made up of clear and colourless plagioclase, with well- 

 marked twins and extinction-angles of 14° to 17° (agreeing with 

 oligoclase) on either side of the trace of the plane of composition. 

 ' A thin section, cut from a specimen showing the contact between' 

 the ' Band ' and the mass of limestone which appears to be included 

 in it, exhibits points of interest. The aspect of the * Band ' is 

 greatly altered. It is fine-grained, rather pink in colour, and 

 discloses no distinctive minerals when examined by the naked eye. 

 The limestone is not so coarse as in the cutting nearer Fkuwela, 



